Large amounts of the greenhouse gas methane can be produced at the bottom of reservoirs. In order to limit its climate-damaging effect, researchers have now developed a system with which the gas-laden sediment can be removed from the reservoir like a vacuum cleaner. The methane is separated and can be used to generate electricity – for example to drive the vacuum cleaner. However, the “methane vacuum cleaner” is still a long way from being ready for the market.
In reservoirs, more organic material such as leaves collects because the natural flow of water is blocked by the damming. If microorganisms on the bottom of the lake break down this organic material under low-oxygen conditions, larger amounts of methane are produced. This potent greenhouse gas is around 30 times more harmful to the climate than the same amount of carbon dioxide. The Wupper Vorsperre alone releases as many greenhouse gases every year as a car emits over a million kilometers.
A methane vacuum cleaner for reservoirs
A research team from the Technical University of Cologne has been working on a solution to this problem for some time and has now been able to further optimize a corresponding prototype. It is a high-pressure suction device attached to a floating platform. The sucker loosens the sediment from the lake and brings it up to the platform together with water and gas, where the mixture is broken down into its components. The methane gas is discharged and the remaining sediment then ends up in the river below the dam, where it is no longer a very productive source of methane.
Compared to the previous prototype, the new “vacuum cleaner” model is significantly more powerful and efficient, as the scientists report. The gas that is brought up can now be stored, for example, in four special containers with flexible plastic film that are mounted on the floating platform. Each of them has a capacity of 250 liters. In addition, project manager Christian Jokiel and his team have installed a converted petrol generator on the platform, which can generate electrical energy from the collected gas. In this way, the gas can not only be diverted from its path into the atmosphere, but also used energetically.
It’s still a long time before it’s ready for the market
To test the latest prototype, the research team conducted 36 test drives on the Wupper Vorsperre, a dam with a volume of 307,000 cubic meters. The tests were promising. “We extracted an average of 120 liters of gas with an average methane content of 50 percent. A total of 3,047 kilojoules of energy could be generated from these 4,322 liters of gas,” reports Julia Außem from SedimentWorks GmbH, the project partner of TH Köln.
In the future, this electricity could be used directly to operate the “methane vacuum cleaner”. Extrapolations showed that the energy generated from the methane would cover at least 31 percent of the energy required to operate the device. The platform would therefore collect methane, generate energy from it and continue to use it to propel itself.
However, there is still a long way to go for the TH Köln system to be ready for the market. “Gas analysis and storage must be further optimized for commercial use. The gas could also be used in local biogas plants, for example. The platform itself could extract even more methane gas from bodies of water than before through automation and smaller dimensions,” explains project manager Jokiel. All of these aspects are to be further optimized in the future so that the methane extractor can be used on reservoirs throughout Germany.
Source: Technical University of Cologne